Process for conserving heat in steam-power plants



S. IVI. LILLIE.

PROCESS FOR CONSEHVI NG HEAT TAI STEAM POWER PLANTS.

APPLICATION FILED APR.23, Ism.

. f WEZ W AI UNITED STATE PATENT OFFICE.

PROCESS FOR CONSERVINGHEAT IN STEAM-POWER PLANTS.

Specification of Letters Patent.

Patented Oct. 18, 1921.

Application filed April 23, 1918. Serial No. 230,255.

To all whom 'it' may concern.' Y

Be it known that l, SAMUEL MORRIS LILLIE, a citizen o-f the UnitedStates, residing at Philadelphia, in the county of Philadelphia andState of Pennsylvania, have invented a new and useful Process forConserving Heat in Steam-Power Plants, Notably in Those of PublicUtilties Companies, which process and apparatus are set forth in thefollowing specification, in which reference is had to the accompanyingdraw- 1n s.

n the operationl of power plants in which the heat agent is steamfurnished by steam boilers it is the practice to blow down or away waterfrom the boilers at intervals to remove impurities which become'concentrated in the boilers due to the evaporation of the feed waterwith which the boilers are supplied to replace that leaving the boilersas steam, as blow down waters or as other escaping water. The blow downwater leaves the boilers at boiler temperature and the feed water isinitially much below the boiler water temperature. As a. rule the feedwaten. before being passed into the boilers is heated partway to boilertemperature by various means; exhaust steam from steam motors, and fluegases from the boilers are among those commonly used. y

An object of my invention is to return to the steam producing system theheat taken from the boilers with the blow down water and in any watertaken from the boiler in addition which the practising of my process maymake desirable, Another object of my invention is to return to theboilers practically all of the blow down7 water, but in the purer formof -distilled water. Still another object is to deliver back into thesystem heat from auxiliary exhaust steam after the heat has been firstemployed for a useful purpose.

The first object is attained by leading the blow down water, as itleaves the boilers, into an inclosed space in which a pressureis'maintained less than that corresponding to the temperature at whichthe water comes to the'space, in virtue of which a portion of the blowdown water flashes into steam, and by delivering the heat in the flashsteam into the feed water for the boilers, either by condensing theflash steam in the feed water, or by intermediate means, such as asurface heater through which the feed water flows and in which the flashsteam agent. Incidentally to this proceeding is the employmenty of theheat in the flash steam for some useful purpose which does not preventthe heat from continuing on to the feed water. The highest point, atwhich, 1n the course of the heating of the feed water, this flash heatmay be delivered to the feed. water will depend upon the pressuremaintained in the said inclosed space. If this pressure be above thatcorresponding to the temperature at which the feed water leaves the lastof the other means for heatmg 1t', some at least of the heat in theflash is the heating steam may be the last heat put into the feed' watenbefore it enters the boilers.

In this application, an example of the use ful employment of the flashsteam heat o n its way to the feed water, is the evaporation ofi waterby the heat to produce make up feed for the boilers, and to realizeanother object of my invention the blow down water is the wat-erevaporated by the heat in the flash steam which has come from itself;the vapors from this evaporation are condensed by the feed water and itsheat passes into the latter and also the distilled water resulting fromthe condensation. Therefore with the exception of a trifle of the blowdown water which is not evaporated, all of it 'and all of the heat itcontained is delivered into the feed water and thereby returned to theboilers. The auxiliary exhaust steam heat is also used to evaporatewater and in the resulting vapors it is used for heating feed water.

Referring to the drawings A, A, A, indicate three of a set of boilers;the Babcock and Wilcox water tube type are shown. The casing at the rearor down flow end of one of the boilers is removed to expose to view thesteam drum B above, the mud drum C below and also the down flow pipes o,and headers L of the evaporating tubes, which together connect the steamdrum to the mud drum. Each of the boilers has a blow down pipe a, whichpipe has ya valve fitted branch c, to the mud drum C, and a similarbranch b to the steam drum B, which enters the latter through itsunderside near the down flow pipes 0. Each blow down pipe a, dischargesthrough a graduated control valve d, into a T D, through one of its runends, the opposite end of which is closed by a removable and replaceableblank flange c.'

The branch of each T D, connects through a valve e, with a branch of themanifold iash main E, that'leads to the branch of the vertical run Twhich connects from the upper end by e pipe 1, with the reduced pressuretank F through its top side, and the T from its lower end by the pipe 2connects through one end of the said tank near the bottom of the latter.

A steam motor represented by the turbine T, receives operating steamfrom the boilers A, through a steam main U, having branches u, one toeach of the boilers A: this main and its branches are provided withproper control valves. An exhaust steam line X y leads from the turbineT through the casing of a surface condenser W, through whose tubes acooling water is passed to condense the exhaust steam on the outersurfaces of the tubes. The case of the condenser opens below into a wellV, into which the condensate falls and from which a boiler feed pump P,draws through the connecting pipe d. The condensate which falls intothis well is somewhat cooler than urated steam at the pressuremaintained on the condensate side of the condenser tubes. This pump Pdelivers by the pipe 'v' to and through an auxiliary surface condenser Nand the'n through feed water heaters (not shown)" into the boilers A, byconnecting branches to the several boilers.

From the top of the reduced pressure tank F leads a vapor main G, iittedwith a safety valve 3. `The main G connects through the branch H fittedwithvalve 4 to an evaporator I', which is indicated as the hottesteffect of a'triple-eifect I", I2, I, and it connects through itscontinuation J fitted with the valve 9 with the cross 22 and through thebranchesL and M of the cross, fitted with stop valves 11 and 12respectively, the main G may be connected with either the main condenserW or the anxiliary condenser N or. with both. The cross 22 also isconnected with the evaporatiug chamber of the effect I3 through thevapor main K fitted with the stop valve 10. The bodies or effects ofthis tripleeiect are all of similar construction. This construction andthe connections between the eects of the tripleeifect are such that whenin Service the steam, for evaporation, enters the steam end P of thehottest effect and` thence paes f into slightly upward inclined tubes,each closed at .its far end, which project through a separating tbeplate into an evaporating chamber in which the tubes are surrounded bywater from which water evaporation is eected by theesteam in the tubes.The vapor of eva ration passes from the evaporating cham r of effect Iby the main 5 into the steam end I2 of the intermediate 65 e'ect andcauses evaporation in its' evapo the temperature which corresponds tosat? rating chamber from water inthe latter. The vapor from .theintermediate eect passes through the main 6 into the steam end E3 of thethird and coolest edect, in which this vapor causes evaporation fromwater in its evaporating chamber. The condensate in the case 'of eacheiect flows from its tubes into the steam chamber of the eil'ect. Thevapor from the evaporating chamber of the third eiect passes through thevapor main K either through the main L into the main condenser W, orinto the auxiliary condenser through the branch main M, or through bothof these branch mains partly into each of the two condensers. A pipe mleads from the bottom'of the auxiliary condenser N into the maincondenser well V, which pipe serves to pass the condensate of thecondenser N into the well V, and also to pass any incondensible gasesinto the well V, any vapors which may pass with the gases assist inheating the eenden/sate from condenser A vacuum pump VP connected withthe Well V of the condenser W by the pipe 23 serves to draw theincondensible gases from the condenser to maintain the vacuum in thesame. The contlensates from the steaml ends, l', I2, I3, of the effectsare delivered into the well V, of the condenser, W, and forms a part ofthe boiler feed as through the pipes 7, 8, m and e an', for example. Apipe g, fitted withstop ifalve 19, connects to the vapor main system atthe cross H, and affords means of delivery to the system steam fromother sources than the boiler blow down waters, auxiliary exhaust steamas from a pump R, for example.4

Methods of operating the illustrative apparatus of the drawings toobtain the pur- 105 poses o my invention are as follows:

Water is drawn from each boiler concerned in the operation through itsblow udown pipe a, as re ated by its indexed Hvalve d, into its T Thewater may be 110 drawn from the mud drum C alone through the pipe c, orfrom the steam drum B alone, through the pipe d, in which latter case it1s impossible to lower the water in the boiler suiclently to uncover anyof its tube surv faces. in the water may be drawn simultaneously fromboth drums. .The water and vapor from all Ts D pass through the openvalves e, into the flash main E, and thence into the reduced pressuretank F via the T f, in which a lower pressure `than that in the boilersis'maintained by the condensation of flash steam in the evaporator I, orin the condensers N or W as hereinafter described.

The reduced pressure in tank F is communicated back into the main E, andalso into the Ts D, in the last to degrees which may be controlledseverally by the valves d.' There is some flash steam formed in these13p Ts. The main E and T f, are assumed to be large enough so that theflashing of the water into steam, due to the lower pressure, i

face of the water in the tank.- The plate 7',

and the space in the upper part of the tank F, free the vapors passingthroughvof any yundue amount of entrained water; r1`he pressures in theTs D, by'means of the valves e, are kept about equal and enough lowerthan the pressures in the boilers so that slight differences in pressurebetween the several boilers will have practically no ef-` fect on therelative flows of water from the boilers into the Ts D, when the systemis operating with continuous flows from the ',boilers.

A preferred way of operating this apparatus is one which transfers intothe feed water for the boilers nearly all the heat contained in the blowdown water taken from the boilers, and nearly all the water` itself, butin form of distilled water. Operatmg for these purposes waters are takencontinuously from the boilers through lthe indexed valves a3,respectively set so that the flow of water from the different boilerswill be about proportionate to their rates of evaporation. The vaporfrom 'the reduced pressure tank F is passed into evaporator I and isemployed in the triple effect to evaporate the blow down water whichpasses from the tank F` into the evaporator I by the pipes s, ascontrolled by the valve 20, unless the How is automatically controlledby the evaporator, in which case the valve 2O is kept wide open. Thismultlple eHect is supposed to befitted with the customaryinter-connecting pipes and valves between the effects, so -that eacheffect, save the hottest one, receives its supply of water to beevaporated from the next hotter effect, from which it follows that theimpurities concentrated by evaporation collect in the water in thecoolest effect I3, which water may be kept below any desired degree ofconcentration .by venting the impure water from the effect constantly oroccasionally through the vent pipe e. Apart from radiation losses this fvented water contains all the heat of the boiler blow down water, or forthat matter of any other heat that may be used for evaporation, that islost.

This loss is small in amount but might be mostly saved by using it in aheat transferrer of any kind for heating the make-up water, if colder,which comes to the system from an exterior source.

The vapors from the coolest effect I3 may pass throughI the mains K andM into the auxiliary condenser N, or through the main L into the well Vof the main condenser W. In either case its heat is transferred to thefeed water from the boiler. With respect to the vapor which may be sentinto the well V should not be more than sufficient to heat thecondensate falling from the condenser tubes, of the condenser, W, higherthan a little below the temperature corresponding to the pressurecarried in the condenser, for if the amount of vapor passed exceedsthis,

some of it is likely topbe condensed on the surfaces of the tubes andthe heat of this portion be carried away in the cooling water of thecondenser. he amount of feed water make up is, of course, greater thanthe blow down water, and consequently some water from an extraneoussource has to be added to the blow down water to permit of sufficientdistilled water being' obtained to furnish the entire make up feed waterneeded. This extraneous water `may be added to the blow down water inthe reduced pressure tank F, through the pipe n, leading into the tank:this pipe is fitted with a stop valve 13 and also a balanced valve 14:which is automatically operated by a float resting on the surface of thewater in the tank F by which the inflow of the said water is made tokeep pace with the extra evaporation needed to furnish the make up, thisadded water might be introduced directly into evaporator I though thepipe z', fitted to the stop valve 16. With a sufficient number ofeffects in the multiple effect, the flash steam from the 'blow downwaters may be made alone sufficient to not only evaporate itself, butalso the added water. In case of a smaller number of effects, thedeficiency in the flash steam may be made up by auxiliary exhaust steamtaken into the multiple effect through the pipe g asn controlled by thestop valve 19.

By the method of operating just described all of the heat and all of thewater leaving the boilers in the blow down waters is with but slightloss transferred to the boiler feed water and returned to the boilers,and this is also the case with any heat which enters the multiple effectwith the auxiliary exhaust steam. It is apparent that by the transfer ofall the blow down water into the feed water in the boilers, aconsiderable saving in water is effected, which may be of consequence inarid regions.

In cases where it may not be necessary' steam by the feed water itselfwithout the intervention of an evaporator. For example, in the apparatusof the drawings the triple eH'ect Il, l2, 13 could be cut out b yclosing the valves in the connections to 1t and opening the valve 9 inthe main J and either one or both of the valves 11 and 12 in the mains Land M, leading respectively to the main condenser W and to the auxiliarycondenser il, in which the Hash steam would be condensed by the feedwater and its heat imparted to the latter, and its condensate would beadded to the feed water by the pipe M', in the case of the lattercondenser. lit all ot the Hash steam may be condensed in the well of thecondenser W, without raising the temperature of the water above thatcorresponding to the pressure in` transferred to the extraneous make upfeed water, if the latter befcooler than the former. l

It is often the case in a power plant that there are a number of'imainturbines each supplied with steam from its own battery boilers. ln sucha power plant there might, of course, be an evaporating outfit similarto this described herein, for each unit of turbine and boilers, but onelarge evaporator unit might be made to serve for all the boilers of theplant by having the Hash down system for each set of boilers andconveying the Hash steam .from each to the evaporators, for example, ifthe power unit and boilers shown in' the drawings were one of a number,the Hash steam from the other power units might be brought to the tripleeH'ect Il, l2, 13 through the pme g to whlch Hash steam connectionswould bring the Hash steam from the other units. The blow down watersfrom the reduced pressure tanks F of the other units could be brought tothe triple etl'ect by pipe Connections Z, leading to the pipes 1.

In the foregoing a continuous How of the blow-down waters from theyboilers is assumed, but with intermittent blowfdowns Howing as theycome into the Hashing down means, a recovery of heat and of water may beobtained. With intermittent blowdowns a continuous How of the blow-downwaters may still be had t0 the flashing down system by sending theblow-down waters into a closed storage tank located below the boilers inwhich a suiiciently lower presmaestro sure, than boiler pressure, ismaintained to permit the blow-down waters to discharge into it.

ln the drawings the condensate and vincondensible gases of the auxiliarycondenser N, pass through the pipe m into the main condenser well V, inwhich the pressure is lower. This condensate and these incondensiblegases might of course be taken away :from the condenser N, byindependent suitable pumps, as it is customarily done for surfacecondensers.

`plhe heat in the blow-down waters might be used in a modified way forevaporating while on its way to the feed water, z'. e. by sending thehot blow down waters through the tubes of an evaporator, arranged withan inlet and outlet for the blow-down waters similar, for example, tothe arrangement of the tubes in the condenser W of the drawings, withthe water to be evaporated covering the exteriors of' the tubes. If theevaporation in the evaporator were proceeding under atmosphericpressure, the blowdown water might be cooled nearly to the correspondingtemperature of 212 F.; the cooled blow-down waters could be deliveredback into the evaporator as the water to be evaporated.

By waste steam heat where employed in the following claims, is to beunderstood as heat which had been imparted to the water in the boilers,and which would'` be discharged away from the system to waste, un-

less employed for some useful purpose, or returned by. some means to theboiler system. Examples of such heat are found in the blowdown watersand in the exhaust steam from auxiliaries in power plants.

ll claim as my invention:

1. The process of utilizing heat in hot water in steam power plantsconsisting in leading it into a space in which is'maintained a lowerpressure than the pressure corresponding to the temperature of thewater, in employing the resulting Hash vapors in an evaporating plant toevaporate water for the production of vapor and distilled water, and

in using the vapors for heating the feed water for the boilers.

2,I The process ofutilizing the heat in hot Water drawn from steamboilers consisting in leading it into a space in which is maintained alower pressure than, the pressure corresponding to the temperature ofthe -water, in employing the resulting Hash vapors in an evaporatingplant to evaporate water for the production of vapor and distilledwater, and in delivering the distilled water into the boilers.^

l 3. The process of utilizing the heat in hot water drawn fromsteam`boilers consisting in leading it into a space in which ismaintained a lower pressure than the pressure corresponding.. to thetemperature of the Water, in employing the resulting ash vapors in anevaporating plant to evaporate Water for the production of vapor anddistilled Water, in using the vapors for heating the feed Water for theboilers, and in delivering the distilled Water into the boilers.

4. The process of utilizing the heat in hot Water taken from steamboilers, such as blowdown Waters, consisting in employing a portion ofits heat in a suitable evaporator for evaporating Water to producevapor, in using the partially cooled Water drawn from the boilers as thesaid Water evaporated, andfin using the vapor formed for heating feedWater for the boilers.

5. The process of returning heat and Water contained in heated Waterobtained from the steam boilers of steam power plants back into thesteam boilers consisting, first, in evaporating the heated Water intovapor,

second, in cooling and condensing the said` vapor by the feed Water forthe steam boilers1 third, in adding to the said feed Water thecondensate obtained by the said cooling and condensing the vapor, and,fourth, in delivering the feed Water thus heated and added to into thesteam boilers.

6: The process of utilizingA heat in hot Water drawn from the boilers,consisting in drawing the said Water from the boilers, ina continuousand practically uniform stream, and in employing the heat forevaporating water for the productionV of distilled Water, and indelivering the distilled Water into the boilers'.

S. MORRIS LILLIE.

